Search antenna system



July 1, 1969 J. B. GARRISON SEARCH ANTENNA SYSTEM Filed Oct. 29, 1964 AXIS OF ROTATION FIG. 1.

PLANAR COMPUTING LE NS SWITCH MATRIX FIG. 2.

JOHN B. GARRIS ON IN VEN'TOR.

A TTORNE Y United States Patent U.S. Cl. 343854 5 Claims The present invention relates in general to antennas and, more particularly, to an omnidirectional antenna system in which both the azimuth and elevation of the radiated beam may be rapidly varied.

The instant invention is intended to be compatible with the antenna system disclosed in the copending application of John B. Garrison, Ser. No. 20,231, filed Apr. 5, 1960, and assigned to the United States Government. The antenna system described in this copending application is part of an overall weapons system which simultaneously provides multiple target tracking and weapons guidance. Such a system requires a high power, spherically symmetric antenna having an extremely rapid beam shifting capacity.

While the antenna system described in the above-mentioned application is the preferred embodiment for use with the overall weapons system, it has been found to be much too large to be carried by smaller class ships. Since the heart of that antenna system is a Luneberg lens, which can not be reduced in size without incurring a serious loss in resolution, it was found necessary to develop another antenna system of smaller size but compatible with the weapons system.

It is therefore an object of the present invention to provide an antenna system which is capable of rapid beam shifting with high resolution among multiple targets.

It is another object of the present invention to provide an antenna having both mechanical and electrical beam rotation, whereby omnidirectional scan coverage is obtained.

These and other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a pictorial representation of the antenna according to the present invention; and

FIG. 2 is a top elevation of the rotary joint of FIG. 1.

The antenna as shown in FIG. 1 consists of a generally cylindrical body having a plurality of radiating elements 11 on its surface parallel to the longitudinal axis of the body. The elements 11 may be formed in any elongated configuration, such as the illustrated segments. As shown, the segments are arranged side-by-side with their straight outer edges defining the outer limits of the body. The body 10 is mounted for rotation with its longitudinal axis horizontal to the surface of the earth. Thus, 360 of azimuth may be scanned by the mechanical rotation of the body, and 90 of elevation may be scanned by the electronic switching of an electric wave between the elements 11, as will be described infra.

The electrical scanning by the elements 11 is accomplished through the use of a planar computing lens 12, of the type described and illustrated in the copending U.S. patent application of Theodore C. Cheston, Ser. No. 187,- 441, filed Apr. 13, 1962, and now U.S. Patent No. 3,230,- 536, issued Jan. 18, 1966 which is assigned to the United States Government. It is sufficient for an understanding of the present invention to note that the computing lens 12 is constructed so as to receive energy at its input feeds, and to distribute this input energy to the output feeds on the opposite side of the lens in such a manner that the phase and amplitude of the energy portions received at the output feeds represent a plane wave directed parallel to a line drawn through the center of the lens from the energized input feed.

The input signals to the lens 12 are provided by a switching circuit or matrix 13 of the type described in the abovementioned copending application of John B. Garrison. The matrix provides pulses to its output leads in a manner determined by its logical design. Each of the output lines from the lens will receive pulses in response to the energization of the appropriate input feeds to the lens by the switching matrix. Each output line of the lens is connected to a high power,-travelling wave tube or equivalent amplifying device 14.

In order to couple the stationary power amplifiers 14 and the computing lens to the line elements 11, a rotary joint 15 is provided, as shown in FIG. 2. The joint comprises an inner movable ring 16 and an outer stationary ring 17, each of the rings being formed of a plurality of waveguide sections 1 through 8. In the actual embodiment a great many more than eight waveguide sections would be employed but, 'to aid in understanding the invention, the number of waveguide sections illustrated has been reduced. Each output line from the computing lens 12 is connected to a different waveguide section of the outer ring 17, and each waveguide section of the inner ring 16 is connected to a different line radiating element 11 through an appropriate coupling means.

To understand the operation of the present invention, assume that the rotary joint is in such a position that the waveguide sections 1 of both the inner ring 16 and the outer ring 17 are in registration. The matrix 13 will selectively apply energy pulses to the input feeds of the computing lens 12, in accordance with the desired elevation of the beam to be generated by the radiating elements 11. As previously mentioned, the computing lens 12 distributes the energy of each input pulse to the output leads or feeds of the lens 12 dependent upon which of its input feeds is energized; i.e., the phase and amplitude of the energy received by the lens output feeds are such as to form a plane wave directed parallel to a line drawn through the center of the lens 12 from the energized input feed. The energy received by the lens output feed that is connected to waveguide section 1 of the ring 17 will propagate into the registering waveguide section 1 of the movable ring 16 and radiate from the element 11 which is electrically connected to this section of ring 16; whereas, the energy received by the lens output feed that is connected to waveguide section 2 of ring 17 will be radiated from the element 11 which is connected to section 2 of ring 16, etc. In other words a radiated beam will be generated by the elements 11 at an elevation dependent upon the selective energization of the input feeds to lens 12. Thus, by the logical switching of the matrix 13, the beam may be steered in elevation through a scan angle of without the necessity of rotating the joint 15.

Assume now that the antenna is rotated so that waveguide section 1 of the outer ring 17 is in registration with waveguide section 3 of the inner ring 16. It is to be noted that the azimuthal direction of the beam will be varied by an angle equal to the angular rotation of the rotary joint. Also, the coupling of the waveguide sections will be changed so that a different radiating element 11 is now coupled to the output of the planar computing lens. Thus, the rotation of the rotary joint will enable the radiated beam to be varied in elevation without the necessity of switching the output of the matrix 13.

From the above description it will be obvious that the combined effect of rotating the rotary joint 15 and selectively energizing the input feeds to the computing lens 12 enables the antenna of the present invention to radiate a beam at any desired elevation and azimuth. In other words, the proposed antenna is capable of omnidirectional scan.

The phase requirements of the computing lens, as fully discussed in the above-mentioned Patent No. 3,230,536 to Theodore C. Cheston, are such that the incremental phase difierence between adjacent output terminals of the lens 12 may be as great as 180". If the transmitter were pulsed to cause the antenna to radiate when the rings 16 and 17 were misaligned, the two out-of-phase signals will be coupled into one of the waveguide sections of the movable ring 16. The resulting power loss due to phase cancellation is, of course, highly undesirable, but may be avoided by permitting the rotation of the antenna to control the pulse timing of the transmitter. The antenna pulsing system is so designed that the antenna will not be pulsed for transmission when the rotary joint is misaligned. Pulse timing systems compatible with the present invention are well-known.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An antenna system comprising:

means for providing a planar wavefront of electromagnetic energy,

a plurality of radiating elements arranged to constitute a generally cylindrical body having a horizontal axis of circular symmetry, said body being rotatable about an axis perpendicular to said horizontal axis,

each of said elements being oriented to radiate electromagnetic energy at a different elevation, and

' coupling means operably connected to said planar wavefront providing means for supplying said electromagnetic energy to said radiating elements in accordance with the phase and' amplitude relationship necessary to cause said plurality of radiating elements to radiate a beam of energy directed in a selected elevation, whereby said beam may be radiated in substantially any desired direction as said cylindrical body rotates.

2. The antenna system of claim 1, in which the coupling means comprises a pair of circular concentric rings,

each ring containing a number of waveguide sections equal to the number of said radiating elements.

3. The antenna system of claim 2, in which one of said rings rotates with said. cylinder and the other of said rings remains stationary.

4. The antenna system of claim 3, in which said means for providing a planar wavefront of electromagnetic energy is a planar computing lens having a plurality of outputs equal to the number of waveguide sections in said stationary ring, each of said outputs being connected to a different waveguide section .of said stationary ring, and a plurality of inputs adapted to be selectively energized by input energy in accordance with the desired elevation of said radiated beam.

5. The antenna system specified in claim 4 further including a switching matrix means operably connected to selectively energize the inputs of said planar computing lens.

References Cited UNITED STATES PATENTS 3,230,535 1/1966 Ferrante et al. 343-754 RICHARD A. FARLEY, Primary Examiner.

T. H. TUBBESING, Assistant Examiner.

US. Cl. X.R. 343-l00, 911 

1. AN ANTENNA SYSTEM COMPRISING: MEANS FOR PROVIDING A PLANAR WAVE FRONT OF ELECTROMAGNETIC ENERGY, A PLURALITY OF RADIATING ELEMENTS ARRANGED TO CONSTITUTE A GENERALLY CYLINDRICAL BODY HAVING A HORIZONTAL AXIS OF CIRCULAR SYMMETRY, SAID BODY BEING ROTATABLE ABOUT AN AXIS PERPENDICULAR TO SAID HORIZONTAL AXIS, EACH OF SAID ELEMENTS BEING ORIENTED TO RADIATE ELECTROMAGNECTIC ENERGY AT A DIFFERENT ELEVATION, AND COUPLING MEANS OPERABLY CONNECTED TO SAID PLANAR WAVEFRONT PROVIDING MEANS FOR SUPPLYING SAID ELECTROMAGNETIC ENERGY TO SAID RADIATING ELEMENTS IN ACCORDANCE WITH THE PHASE AND AMPLITUDE RELATIONSHIP NECESSARY TO CAUSE SAID PLURALITY OF RADIATING ELEMENTS TO RADIATE A BEAM OF ENERGY DIRECTED IN A SELECTED ELEVATION, WHEREBY SAID BEAM MAY BE RADIATED IN SUBSTANTILLY ANY DESIRED DIRECTION AS SAID CYLINDRICAL BODY ROTATES. 